You may come across other so-called facts about training, but you should be aware that some of them are actually fallacies or misconceptions. These oft-quoted statements are not true and have no basis in medical or scientific research.
Fallacy 1: No Pain, No Gain
Although serious training is often difficult and sometimes unpleasant, it shouldn’t actually hurt. Here is an important distinction: Pain is not a natural consequence of exercise or training; it signals a problem that you need to address. In fact, well-prepared athletes sometimes perform in a state of euphoria, free of pain and oblivious to discomfort. Think about it: You’ve probably seen the end of a long-distance race where the winner finishes full of life even though the rest of the field appears wasted. This is made possible by the fact that when you exercise, your body produces natural opiates (endorphins) that can mask discomfort of the effort. But if you suffer real pain while training, back off. And if the pain persists, get it evaluated.
All of this notwithstanding, discomfort can accompany difficult training such as heavy lifting, intense interval training, and long-distance work. This discomfort (as distinct from pain) results naturally from the lactic acid that accompanies the anaerobic effort of lifting or doing intense intervals—and of the muscle fatigue, microscopic muscle damage, and soreness that come with long-distance training. Thus, whereas I reject the "no pain, no gain" mantra, I accept the following statement: No discomfort, no excellence. Overload is necessary for adaptation, and it sometimes requires you to work at your limit of strength, intensity, or endurance, which certainly can be uncomfortable. But if your exercise results in outright pain, it is probably excessive.